window.onload = function(){
	var li_list = document.getElementsByTagName('li')
	var div_list = document.getElementById('content').children
	for(var i = 0; i < li_list.length;i++){
		li_list[i].index = i
		li_list[i].onclick = clickFun;
	}
	function clickFun(){
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				li_list[j].className = ''
			}
			this.className = 'now';
			for(var k = 0; k < div_list.length;k++){
				div_list[k].className = ''
			}
			div_list[this.index].className = 'current';	
	}
}